Production of Staple Fibers

Even though filament yarns can be made more voluminous and thus more similar to staple fiber yarns by texturing, they do not have the characteristics of typical staple fiber yarns (such as hairiness). Therefore, filaments are often converted into staple fibers either by cutting (prevalent) or tearing. 

Like the cutting of the filament cables within the processing line, the cut converter as well as the tear converter produce a band of single staple fibers as feed material for the next processing steps in the secondary spin processing. In the tear converter, the cables are drawn stepwise to ensure the cohesion of the rope (Fig. 2.62). 

Tear converters are standard in the processing of polyacrylonitrile fibers. 

The torn or cut fibers are processed according to the type of cotton and mainly the worsted or mock-worsted spinning principle (Chapter 3). The staple length is adjusted according to the spinning process. 

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Until the Four Year Plan began, Germany had imported 700,-000,000 Reichsmarks worth of cotton, wool, and other raw textiles every year. But in 1937, Farben s production of staple fibers reached such gigantic figures that the Vorstand could predict their 1938 achievement — more than half of Germany s textile raw materials. 

Early in the manufacture of PP, a concept was developed for dry spinning directly from the solution obtained in the polymerization operation. Had it been feasible, it would have been the realization of a chemical engineer s dream the gaseous olefin fed into one end of the equipment, and the packaged fiber, ready for shipment to a textile mill, coming out the other end. But it did not turn out that way, and today melt spinning is the accepted technique for the production of staple fibers, monofilament, and multifilament yams. To this usual method have been added the fibrillation and the slit film procedures for producing yams. 

Figure 2. Schematic of a typical spin line for the production of staple fibers.

Production of Staple Fiber Yarns with Defined Properties... 

From 1910 onward waste filament yam had been chopped into short lengths suitable for use on the machinery designed to process cotton and wool staples into spun yams. In the 1930s new plants were built specifically to supply the staple fiber markets. During World War II the production of staple matched that of filament, and by 1950, staple viscose was the most important product. The new spun-yam oudets spawned a series of viscose developments aimed at matching the characteristics of wool and cotton more closely. Viscose rayon was, after all, silk-like. Compared with wool it lacked bulk, residence, and abrasion resistance. Compared to cotton, it was weaker, tended to shrink and crease more easily, and had a rather lean, limp hand. 

Approximately 2.5 million t of viscose process regenerated ceUulose fibers were produced in 1990 (Table 1). Measured by production capacity in 1990, the leading producers of filament yams in 1990 were the Soviet Union state-owned factories (255,000 t capacity) and Akzo Fibres in Europe (100,000 t). The leading producers of staple fiber and tow were Courtaulds with 180,000 t capacity spUt between the UK and North America Formosa Chemicals and Fibres Co. with 150,000 t in Taiwan Tenzing with 125,000 t in Austria, and a 40% stake in South Pacific Viscose s 37,000 t Indonesian plant and Grasim Industries in India (125,000 t). BASF s U.S. capacity of 50,000 t was acquired by Tenzing in 1992. 

Other Fiber Deformations. Deformations such as bending, torsion, shear, and compression are of practical importance in textile apphcations. Bending and twisting of yams, both influential in the development of bulk and stretch in filament yams, are also important in the production of staple yams. Bending characteristics are important in cmsh resistance in carpets. Bending and shear are factors that influence the hand and drape of apparel fabrics, whereas compression influences the recovery of fabrics after such processes as winding. 

In 1994, the proportion of PET fibers in the world production of synthetic fibers was 62.9% and of chemical fibers was 55.3%, while in the total volume of all kinds of fibers it was 27.4%. Out of PET fibers presently produced, 38% are staple fibers and 52.5% are filament yarns, with a marked tendency toward an increase in the latter. A 55% proportion is anticipated in the year 2000, At present, about 75% of PET fibers are used for textile purposes and 25% for nontextile purposes. 

The spinnability and spinning properties of a polymer are of the highest importance in the manufacturing of staple fibers and filaments. There are many analogies to the production of films, where breaks or splits are concerned. The frequency of yarn breaks determines the economic viability of the production process, as well as the competitiveness and the reputation of the manufacturer. Today, in the age of automation, it would be theoretically possible to manage the processing of the polymer with a minimum of staff if no yam breaks disturbed the processing. 

Different degrees of dyeability of staple fibers and filaments for textile applications seriously affect the constancy of product quality. This phenomenon has become more or less a matter of industrial production experience. Only a few... 

Properties of Staple Fibers. Fiber diameters range from AAA lo G (Table 2). with the largest production volume in the range C—G. Thermal conductivity of gluss-liber products is influenced by fiber diameter, density or compactness of the liber mass, and temperature conditions. Generally, thermal eunductiv itv ranges between 0.20 and 0.80 (Blu)lin.)f(hr>Ht It F). In metric units. I his is 0.02y and 0.1 15 watl/meter-Kclvin W/ni K. 

Rope represents a very useful form of fibrous product. A rope or cord consists of a bundle of fibers. The fibers may be continuous or they may be made of staple fibers, i.e. short, fine fibers. The tensile strength of a rope comes from the strength of individual fibers and the friction between them. The interliber friction prevents their slip past one another. Quite obviously, a rope or a cord has very anisotropic properties. It is strong in tension along the axis direction but not in the transverse or radial direction. Strength in compression is also very poor. 

Bundles of yarns from multiple spinnerets are referred to as tow. If the tow is subsequently cut into short specified lengths, it is referred to as staple tow, and the product is staple fiber. Depending on the man-made fiber producer s production equipment, one, two, or all three of the steps just discussed may be executed in either a batchwise or continuous manner. 

In 1981, about one third of the total polypropylene usage was based on conventional staple and multifilament products about 60 KT (thousand tons) of ST and 54.5 KT of multifilament yarn. The largest textile end-use of polypropylene was in carpet backing, which was made primarily from ribbon yams. By 1995, its production surpassed aliphatic polyamides (PA) and polyacrylonitrile (PAN), but lagged behind PET. In 2002, the production of polyester fiber was 62%, polypropylene fiber, 17.5%, polyamide fiber, 11.5%, and polyacrylonitrile, 18.1%i, of all synthetic fibers. 

Table 3.1 presents the worldwide production of polyolefin fibers in 1996 2002, according to Fiber Organon [1]. In 2002, the total production of polyolefin fibers grew to 5.913 million tons (MT). The annual rate of growth was 2% as compared to 8% for polyester, 6.4% for PAN, and 4.4%i for polyamides. The production of polypropylene fibers, excluding fibrillated fibers, reached 3.99 MT in 2002 and 4.20 MT in 2003. About 70% of its production was in filament yarn and 30%i in staple. As Table 3.1 also shows the portion of polypropylene filaments increased from 40.4%i in 1996 to 45.5%i in 2002, while fibers from fibrillating film decreased from 35.2 to 32.5%i. The portion of ST remained steady at 22.1%. 

The purpose of acetalization in the manufacture of PVA fiber is to improve hot-water resistance of the heat-treated fiber further. In the production of monofilament, acetalization is somewhat omitted because the denier of monofilament is low and it can be heat-treated homogeneously at sufficiently high temperature. In the case of staple-fiber production, the total denier of the fiber bundle is high, so it is difficult to realize the homogeneous effect of heat treatment, and the process temperature has to be rather low to avoid local overheating. In most cases, consequently, acetalization is necessary. The conditions for acetalization are as follows ... 

Distribution of Staple Fiber Products by Fiber Type for 1994 ... 

U.S. production of staple and tow for 1965-1996 is shown in Figure 12.53 [691]. The data clearly show the rise in polyester as the dominant fiber, beginning in 1965 and peaking by 1980. The data also show that acrylic enjoyed its best years in the late 1970s, with the decline in the carpet market starting in the early 1970s, followed by losses in knit markets beginning... 

FIGURE 12.53 U.S. production of synthetic fiber staple and tow showing the relative quantities of acrylic fiber produced compared to nylon, polyester, and polyolefin. Acrylic production peaked in the late 1970s. One of the major factors was the decline of the acrylic carpet market, now dominated by nylon. (From Manufactured Fiber Producer Handbook, 1996 Fiber Organon, February 1997, Fiber Economics Bureau, pub.)... 

The most important application of nylons is in production of synthetic fibers. Nylon fibers are largely produced in the form of continuous filament yam and staple fiber. Since fibers should simultaneously possess crystallization and... 

Uniaxial orientation n. An orientation process that stretches the product in only one direction, as in manufacture of staple fiber, monofilaments, and melt-cast film. 

Approximately 3 million metric tons of regenerated cellulose fibers production capacity existed in 2000 (Table 2). The leading producers of filament yams were the Chinese state-owned factories (118,000-t capacity), Acordis in Europe (69,0001), and the Russian plants (with 44,000 t). The leading producers of staple fiber and tow were the Chinese with 480,0001, the Birla Group (India) with 408,0001, Lenz-ing (Austria, U.S.A., and Indonesia) with 315,000 t and Acordis with 170,000-t capacity split between the United Kingdom and North America, Formosa Chemicals and Fibers Co. with 162,000 t (in Taiwan). Acordis was formed in 1998 from the fiber businesses of Courtaulds and Akzo-Nobel following the takeover of Cour-taulds by Akzo, who later sold Acordis to a consortium of CVC Partners and Acordis management. (Note since these statistics were compiled, 100,000 ton of Acordis s viscose staple fiber capacity has closed.)... 

Most acrylic fibers are wet-spun, but dry spinning is also applied. The most common solvent is dimethylformamide, DMF. The polymerization of acrylics can also be carried out in DMF and the polymerization solution can then be directly spun. The boiling point of DMF is 153°C, making complete removal of solvent in the spinning column almost impossible. Most dry-spun acrylic production is staple fiber, and the remaining solvent is then removed during tow processing. 

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